[SSJup81]

Originally Posted by auranoir

thanks! that clarifies a lot, but I got a little confused with your example.

in the first example 'white' serves as an adjective. but the Japanese don't say shiroi there. but generally otherwise they would use shiroi?

What is your favorite color?
White - thus shiro

but

I need to buy a white shirt. - white-colored - thus 'shiroi'

am I understand this right or are there some exceptions I should know of?

Yeah, pretty much. In that instance, you would use "shiroi" as opposed to "shiro" because "white" is being used as an adjective (白いシャツ).

Originally Posted by SceptileMaster

Does this apply to other adjectives other than colours?

Probably only the ones that can be nouns and adjectives, which only colors seem to fall into. I honestly can't think of any other adjective (outside of colors, like in the examples) that can be used as a noun as well. I could be wrong though.